1. Field of the Invention
The present invention relates to a display apparatus displaying, on a common display screen, different images in respective directions.
2. Description of the Related Art
There have been proposed display apparatuses which can display, on a common display screen, different images in respective directions (i.e. DV (dual view) display).
FIG. 14 is a schematic cross section showing an example of such display apparatuses. The display apparatus shown in the figure includes a display panel 110, a barrier section 120, a backlight 130, and polarizing plates 141 and 142.
The backlight 130 is provided with a light source 131 and a reflection section 132 as shown in FIG. 14, and causes the display panel 110 to be irradiated with light in such a manner that the reflection section 132 reflects light emitted from the light source 131.
The display panel 110 is an active matrix liquid crystal display panel in which a liquid crystal layer 113 is sandwiched between a TFT substrate 111 and a CF substrate 112 opposing to each other.
The surface of the TFT substrate 111 is provided with plural data signal lines and plural scanning signal lines intersecting with the respective data signal lines. At each of the intersections between the data signal lines and scanning signal lines, a pixel is formed (none of these members are illustrated). The data signal lines and the scanning signal lines are connected to a source driver and a gate driver (none of them are illustrated), respectively. With this arrangement, a drive voltage is independently applied to each pixel so that alignment of liquid crystal molecules in each pixel area of the liquid crystal layer 113 is changed, and hence image display is achieved.
As shown in FIG. 14, the pixels are arranged in such a manner that, along the data signal lines, lines L of pixels for image display for the left side of the display apparatus and lines R of pixels for image display for the right side of the display apparatus are alternately provided.
The CF (Color Filter) substrate 112 has a color filter layer (not illustrated).
The TFT substrate 111 and the CF substrate 112 are provided with orientation films (not illustrated) on their surfaces opposing to each other. The orientation films are oriented in perpendicular directions, and each orientation film is rubbed in a direction parallel to the substrate surface. The polarizing plate 141 is provided on the backlight 130 side of the TFT substrate 111 in such a manner that the absorption axis direction of the polarizing plate 141 is parallel to the orientation of the orientation film on the TFT substrate 111. The polarizing plate 142 is provided on the display surface side of the barrier section 120 (i.e., on the opposite side to the backlight 130), in such a manner that the absorption axis of the polarizing plate 142 is perpendicular to the absorption axis of the polarizing plate 141. With this arrangement, a drive voltage applied to each pixel is changed so that each line of pixels can perform display for each display direction.
The barrier section 120 is constituted by a barrier glass 121, a barrier light shielding layer 122, and a resin layer 123. The barrier light shielding layer 122 shields against parts of light emitted from the backlight 130 and passing through the display panel 110. The resin layer 123 is formed on the barrier glass 121 so as to cover the barrier light shielding layer 122, and connects the barrier section 120 with the display panel 110.
The barrier light shielding layer 122 is provided so as to form stripes corresponding to the respective lines of pixels. That is to say, the stripes of the barrier light shielding layer 122 are formed to shield against parts of light emitted from the backlight 130 and passing through the lines of pixels, in such a manner as (i) to cause the lines L of pixels for the left side to be observable from the left side of the display apparatus but not to be observable from the right side of the display apparatus, and (ii) to cause the lines R of pixels for the right side to be observable from the right side of the display apparatus but not to be observable from the left side of the display apparatus. As a result, the display apparatus can display different images for the left and right sides of the display apparatus (i.e., can perform DV display).
In the meanwhile, for example, U.S. Pat. No. 5,883,739 discloses a vehicle information display apparatus in which left-viewpoint image and right-viewpoint image for the driver's seat and left-viewpoint image and right-viewpoint image for the passenger seat are alternately arranged by pixel and synthesized, so that a stereoscopic image is viewable from the driver's seat and the passenger seat.
This document also teaches that, the left-viewpoint and right-viewpoint images for the driver's seat are made blank and synthesized with the left-viewpoint and right-viewpoint images for the passenger seat, with the result that a stereoscopic image cannot be viewed from the driver's seat and only viewable from the passenger seat.
U.S. Pat. No. 6,445,434 discloses a liquid crystal display apparatus including a liquid crystal layer, an orientation film by which the liquid crystal layer is oriented, and a drive circuit driving the liquid crystal layer, wherein the orientation film is divided into plural areas each of which has a visible size and a particular shape, and orientations of neighboring areas are different from one another.
In this liquid crystal display apparatus, a displayed content is hardly viewable in all directions except a case where the liquid crystal display apparatus is viewed head-on, on account of the arrangement above. Also, since a predetermined pattern is viewed in directions other than the head-on direction, a figure or a product name may be presented to the viewer.
U.S. Pat. No. 6,445,434 also teaches that two liquid crystal layers (upper liquid crystal layer and lower liquid crystal layer) are provided, and the lower liquid crystal layer which is farther away from the viewer is used for regular display whereas the upper liquid crystal layer is used for switching between a state where the display by the lower liquid crystal layer is viewable in directions other than the head-on direction and a state where the aforesaid display is not viewable in directions other than the head-on direction.
According to this technique, the upper liquid crystal layer has plural areas with different orientations, and the areas are provided so that neighboring areas have different orientations. The upper liquid crystal layer is used for displaying a predetermined figure when viewed in directions other than the head-on direction. With this arrangement, when the upper liquid crystal layer is in a halftone display state, an image displayed on the lower liquid crystal layer is viewable head-on, but, in directions other than the head-on direction, the image on the lower liquid crystal layer is blocked by the figure on the upper liquid crystal layer and hence hardly viewable. Also, after an electric field is applied to the upper liquid crystal layer so that liquid crystal molecules in the upper liquid crystal layer are upright, the image on the lower liquid crystal layer becomes viewable in directions other than the head-on direction.
In the technique of U.S. Pat. No. 6,445,434, however, only a predetermined pattern is viewable in directions other than the head-on direction, or at best, only either the same image as the head-on direction or a predetermined figure is viewable in directions other than the head-on direction. It is therefore impossible to display, by a shared display screen, different images (e.g., moving images) in plural directions.
As discussed above, U.S. Pat. No. 5,883,739 teaches that an image for the driver's seat is made blank when the vehicle is running, with the result that an image cannot be viewed from the driver's seat and is only viewable from the passenger seat.
However, in the display apparatus of U.S. Pat. No. 5,883,739, even if an image for the driver's seat is made blank, an image for the passenger seat may be viewable from the driver's seat, on account of crosstalk. Also in a case where an image for the driver's seat is set to non-display (black display) and only image display for the passenger seat is carried out in a conventional DV display apparatus shown in FIG. 14, the same problem occurs.
That is to say, in the display apparatus of U.S. Pat. No. 5,883,739 and FIG. 14, sets of image light for respective display directions are separated by a parallax barrier which is a conventionally-proposed image separation device. However, when black display for the driver's seat and image display for the passenger seat are performed by a parallax barrier, cross talk of the image for the passenger seat to the driver's seat tends to be obvious. It is therefore necessary to improve the separation capability.
Why such crosstalk occurs will be explained with reference to FIG. 15. FIG. 15 illustrates an example of a display state in which the conventional DV display apparatus shown in FIG. 14 is used as an in-vehicle display apparatus and different images are displayed for the driver's seat and the passenger seat, respectively.
As shown in FIG. 15, in the case where different images are displayed for the driver's seat (right side) and for the passenger seat (left side), among light 150R having passed through lines R of pixels for the right side, sets of light towards the driver's seat reach the driver's seat side through the gaps of the barrier light shielding layer 122, whereas sets of light towards the passenger seat are blocked by the barrier light shielding layer 122. On the other hand, among light 150L having passed through lines L of pixels for the left side, sets of light towards the passenger seat reach the passenger seat through the gaps of the barrier light shielding layer 122, whereas sets of light towards the driver's seat are blocked by the barrier light shielding layer 122. This theoretically makes it possible to separate images (image lights) displayed for the driver's seat and the passenger seat from one another.
In reality, however, scattered/diffracted light 160 is generated because of scatter and diffraction of light at the end surface of the barrier light shielding layer 122, multiple reflection at the layers of the display apparatus, and the like. The scattered/diffracted light 160 is emitted to the display directions so that crosstalk occurs and the separation capability of images is decreased. In other words, while the parallax barrier theoretically makes it possible to separate image lights towards the respective display directions from one another, crosstalk occurs in reality because of diffraction of light at the end surface of the barrier, multiplex reflection at the layers of the display, and the like.
Such crosstalk is relatively unrecognizable when images are displayed for the driver's seat and the passenger seat (i.e., when display for the driver's seat is not black display), but is easily recognizable when display for the driver's seat is black display, as an image for the passenger seat is vaguely leaked to the display for the driver's seat.
FIG. 16 illustrates a case where black display is provided to the driver's seat and an image is only provided to the passenger seat, using the DV display apparatus shown in FIG. 14.
As shown in the figure, in a case where display for the driver's seat is in non-display mode, light 150R having passed through the lines R of pixels for the right side is blocked and cannot pass through the polarizing plate 142. With this, display for the driver's seat is supposed to be non-display. In reality, however, scattered/diffracted light 160 is emitted to the driver's seat. As a result, the image for the passenger seat may be overlapped with the black display for the driver's seat, and a double image may be recognizable.
As such, an in-vehicle DV display apparatus may be required to perform, while the vehicle is running, black display for the driver's seat (i.e., non-display for the driver's seat) and display an image only for the passenger seat. In the conventional art, an image for the passenger seat may vaguely appear on the black display for the driver's seat, and a double image may be recognized from the driver's seat.